Hydraulic systems having hydraulically operated pump and motor are generally operated at high speed or completely turned off as and when desired. For example, engine driven machines such as on-highway trucks, dozers, loaders, excavators etc., include hydraulic systems to cool down the engine temperatures that may have risen during operation. These cooling systems typically include a fan for cooling the engine. However, in situations, where the atmospheric temperature is very low, the engine might not be required to be cooled very much. In fact, a condition of overcooling may be detected in such situations, which is undesirable. Therefore, to prevent the overcooling, the motor may be turned off.